docs: def _package_to_staging(staging_package_url):
      """Repackage this package from local installed location and copy it to GCS.
  
      Args:
        staging_package_url: GCS path.
      """
      import google.datalab.ml as ml
  
      # Find the package root. __file__ is under [package_root]/mltoolbox/_structured_data/this_file
      package_root = os.path.abspath(
          os.path.join(os.path.dirname(__file__), '../../'))
      setup_path = os.path.abspath(
          os.path.join(os.path.dirname(__file__), 'master_setup.py'))
      tar_gz_path = os.path.join(staging_package_url, 'staging', 'trainer.tar.gz')
  
      print('Building package and uploading to %s' % tar_gz_path)
      ml.package_and_copy(package_root, setup_path, tar_gz_path)
  
      return tar_gz_path